An electroluminescent display device such as an organic light emitting diode (OLED) display device has become an important display technology in the display field due to its advantages of wide viewing angle, active illumination, fast response, low power consumption, high luminous efficiency, and flexible display practicality. Meanwhile, an OLED device in the OLED display device is susceptible to invasion of water and oxygen, so that an effective encapsulation structure is needed to prevent water and oxygen from invading into the OLED device. In order to obtain a flexible display device, it has become an important issue in the field of flexible display to improve an impact resistance ability and a bendability of the encapsulation structure.